Hydraulic impact device

ABSTRACT

A HYDRAULIC IMPACT DEVICE WITH AN ALTERNATELY PRESSURE FLUID ACTUATED PISTON AND WITH A CONTROL VALVE FOR CONTROLLING THE IMPACT AND RETURN STROKE OF THE IMPACT PISTION, AND WITH AN IMPACT FORCE STORING HYDRAULIC ACCUMULATOR, IN WHICH THE IMPACT PISTON IS PROVIDED WITH A CENTRAL BLIND HOLE IN FLUID COMMUNICATION WITH A HYDRAULIC ACCUMULATOR ADAPTED INSTANTANEOUSLY TO RELEASE STORED FLUID INTO SAID BLIND HOLE.

Oct. 5, 1971 J. GERBER HYDRAULIC IMPACT DEVICE Filed June 27, 1969 B Q A m w A P 2 2 i 0 ,H E 5 x x 5 m 5 5 v 5 v O V l 4 E 5 United States Patent 6 3,609,969 HYDRAULIC IMPACT DEVICE Jurgen Gerber, Dortmund-Bodelschwiugh, Germany, as-

siguor to Orenstein & Koppel Aktiengesellscliaft, Berlin, Germany Filed June 27, 1969, Ser. No. 837,064 Claims priority, application Germany, July 3, 1968, P 17 03 727.3 Int. Cl. F01l 15/02 US. Cl. 60-51 4 Claims ABSTRACT OF THE DISCLOSURE A hydraulic impact device with an alternately pressure fluid actuated piston and with a control valve for controlling the impact and return stroke of the impact piston, and with an impact force storing hydraulic accumulator, in which the impact piston is provided with a central blind hole in fluid communication with a hydraulic accumulator adapted instantaneously to release stored fluid into said blind hole.

The present invention relates to a hydraulic impact device with a piston which is alternately subjected to pressure fluid and guided in a cylinder, said piston having a mass which is a multiple of the mass of the tool employed for crushing the rock. The device also comprises a control valve for controlling the impact stroke and the return stroke, and furthermore comprises a hydraulic accumulator for storing the impact energy.

Hydraulic impact devices have become known, such as compressed air hammers, for carrying out similar operations. In most instances, fast hammers are involved. With heretofore known hammers, for purposes of obtaining a great number of impacts, there are provided two rotary valves which are driven by a rotary motor which is likewise hydraulically operated. In addition thereto, two pneumatic pressure accumulators are provided for storing energy which is released when the piston moves downwardly while the volume above the piston increases. However, high impact energies as far as the individual impact is concerned, cannot be realized with such a device. Moreover, such device is rather expensive and the control of the rotary valve is liable to disorders.

According to a further heretofore known hydraulic impact tool, a higher impact force is intended to be realized by actuating a spring-loaded working piston by a further piston which is under the influence of an eccentric and which likewise acts upon a spring. Such a system, however, is expensive and, while realizing a fast impact sequence, does not permit a high individual impact energy as it is necessary for special operations, for instance, the crushing of large rocks.

It is, therefore, an object of the present invention. to provide a hydraulic impact device with a high impact energy for each individual impact stroke, in which the device is actuated merely by the hydraulic energy available in a carrier vehicle.

This object and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, illustrating in longitudinal section an embodiment according to the present invention.

The hydraulic impact device with an alternately pressure fluid actuated piston which is guided in a cylinder and has a mass representing a multiple of the mass of the chisel or tool for crushing the rock and with a control valve for controlling the impact stroke and return stroke, and with a hydraulic accumulator for storing the impact energy, is, in conformity with the present invention, char- 3,609,969 Patented Oct. 5, 1971 ice acterized in that the piston is provided with a central axial blind bore for feeding the pressure medium through a pressure pipe while the impact stroke surface of the piston equals the annular return stroke surface, the annular end face of the piston which faces toward the hydraulic accumulator equalling the end face facing toward the inlet end for the tool to be inserted.

The advantage of the arrangement according to the invention is seen in the fact that the delivery of the pump is instantaneously released by means of a hydraulic accumulator and the precisely harmonized conditions of the end faces of the top and bottom side of the piston and the corresponding oil quantities. This release is effected by a positive actuation of the control piston, whereby a high impact force of the individual impact strokes will be realized.

Referring now to the drawing in detail, the cylinder housing 1 is surrounded by a cylinder pipe 2. Between said cylinder housing 1 and said cylinder pipe 2 there is provided an overflow passage 3, a control conduit 4, a line 5 and further devices for conveying the pressure or control oil. The bottom of the cylinder housing 1 and cylinder pipe 2 are closed by a cover 6 which comprises a bore 7 with a tool holder 8. The tool 9 is inserted through a cover 6 and the tool holder 8. The inserted tool is held in the tool receiving piston 10. Guided in the cylinder housing 1 is an impact piston 11 the head 11a of which has a larger diameter than the shank of said piston 11. The upper end of the cylinder housing 1 is closed by an upper housing cover 12 and a covering hood 13. In the upper housing cover 12 there are mounted a pressure pipe 14, a valve spool 15, a relief valve 16, a return spring 18 in a recess 17, and bores for conveying the pressure oil. Above the housing cover 12 there is arranged a hydraulic accumulator 14a which communicates with the pressure conduit 14. The hydraulic pump 19 is through conduit 20, control valve 21, feeding line 22 and conduit 23 connected to the impact device. When turning the impact mechanism off, the oil is in a pressure-free manner conveyed to the reservoir 24.

OPERATION With the control valve 21 occupying the position shown in the drawing and with said control valve assembled in a supporting device together with pump 19, the pump 19 feeds the pressure medium in a pressure-free manner through pump conduit 20 and control valve 21 to the reservoir 24. In order to permit the device to operate, first all chambers have to be filled with oil. To this end, the control valve 21 is moved to the position 11 so that the pump line 20 connects with the reservoir line 23 and the feeding line 22 is connected with the reservoir 24. Consequently, the oil delivery by the pump 19 can through passage 25, discharge line 26 and compensating line 27 pass into the upper cylinder chamber 28 and through the upper overflow bores 40, through the overflow passage 3 formed by the cylinder housing 1 and cylinder line 2, and through overflow bores 41 into the annular passage 43, and through grooves 30 also the annular chamber 41 can be filled. By lifting the relief valve 16 otf its seat, the accumulator 14a and the cylinder chamber 53 communicating with the pressure pipe 14 are filled. The air present in these chambers and the excess oil may through passages 32 and 35, feeding line 22 and control valve 21 flow to the reservoir 24 because the valve spool 15 is lifted by the pressure acting upon its end face 34. After the filling operation has been completed, the relief valve 16 is closed. The device may then be brought into its working position, which means that the tool 9 is placed upon the rock to be crushed, whereby the piston 10 is lifted up to an abutments 63.

' The control valve 21 is then moved to the position I. The device is now in working position and the oil flow will be as follows: The oil delivered by the pump 19 passes through pump conduit 20, control valve 21, feeding line 22, passage 35, passage 36 and conduit to the annular passage 38. In view of the pressure acting upon the annular surface 39 of the impact piston 11, the latter is lifted. The oil pressure in the upper cylinder chamber 28 is passed or forced through the overflow bores 40 and 41 and through the overflow passage 3 displaced into the lower cylinder chamber 50a, 51a. Inasmuch as the upper piston surface 49 of the impact piston 11 has nearly the same size as the lower piston surface consisting of the annular surface 50 and the top surface 51, a nearly pressure-free oil exchange occurs. Since the two end faces 49 and 50, 51 of the impact piston have nearly the same area, also the end face 52 of the working cylinder 53 must substantially equal the annular surface 39. Since in the illustrated position of the valve spool 15 the passage 32 is blocked, the oil present in the working cylinder 53 may nowbe displaced into the accumulator 14a. As a result thereof, the gas in the bag 14b, e.g. air, of the hydraulic accumulator 14a is compressed. When the piston 11 has reached its upper end position, the valve spool 15 is lifted by the lifter 15a so that passage 36 communicates with passage 25, i.e. annular passage 38 with the reservoir 24 on one hand and, on the other hand, passage 32 communicates with passage 35, i.e., pump 19, is connected with the working cylinder 53. Since, however, in view of the fact that the surface 39 is nearly pressure-free, the gas volume in the gas bag 14b expands instantaneously and thus drives the impact piston 11 at very high speed in a downward direction until its pot-shaped recess 51a rides over the step-shaped extension a of the tool receiving piston 10 so that between the extension 10a and the impact piston 11 in recess 51a a closed oil cushion is formed. Since the oil column is to be considered as substantially non-compressible, the impact energy of the impact piston 11 is through the tool receiving piston 10 conveyed to the tool 9. At the same time, however, a pressure simpulse is through bore 55, annular passage 56, bore 57, control conduit 4 and recess 17 conveyed to the valve spool so that the latter returns to the illustratedposition, and the working cycle starts anew. In order to be sure that the valve spool 15 will remain in its lifted position during the downward movement of the impact piston 11, passage 44 and thereby the lower end face 34 of the valve spool 15 communicates through conduit 59 and discharge line 26 as well as through passage with the reservoir conduit 23. Consequently, the damming up pressure prevailing in line 23 will hold the valve spool 15 in its lifted position and will establish communication between the passages 32 and 35.

When the tool 9 during the crushing of the rock does not hit upon any resistance so that the tool receiving piston 10 impacts upon the cover 6, the impact energy is absorbed or destroyed by springs 60 which latter are pre loaded by means of spacer sleeve 61 and screws 62. In this connection the annular passage 56 moves over the bore 57 so that the valve spool 15 cannot reverse instantaneously. The impact sequence, therefore, will become sufliciently slow to avoid any danger of disorders.

It is, of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawing but also comprises any modifications within the scope of the appended claims.

With regard to the opening and closing of the pressure relief valve 16 it may be added that these proceedings take place only for the initial starting of the apparatus and are necessary for the primary filling. By unscrewing of a screw (not represented in the drawing) the tension of the spring of the valve 16 will be released. To shut the valve the screw 'will be screwed down.

It may, furthermore, be added that the instantaneous expansion of the bag 1411 is not interfered with by the pump pressure because the piston 11 is accelerated and the cylinder volume 53 increases, i.e. the cylinder is fed by oil from the bag 14a and from the pump.

What I claim is:

1. A hydraulically operable impact device which includes: a cylinder, a first. cover closing one end of said cylinder, a second cover closing the other end of said cylinder, an impact piston reciprocable in said cylinder and having a blind hole substantially centrally located in that end faceof said piston which faces toward said first cover, the bottom of said blind hole forming the impact stroke surface of said piston, said piston also being provided with a fluid operable piston return surface substantially equaling in area the area of said impact stroke surface, the other end face of said piston which faces toward said second cover having an area nearly equaling the area of said first mentioned end face of said impact piston, a hydraulic accumulator arranged outside said to and from said impact stroke surface and the end faces of said piston, said control valve means including a valve spool having an extension extending into the space between said first cover and the adjacent end face of said impact piston for actuation thereby, and that end face of said piston which faces toward said second cover being provided with a recess forming an auxiliary cylinder, said device also including tool holding means having an extension adapted slidably to be received in said auxiliary cylinder, and conduit means leading from said control valve means to said auxiliary cylinder.

2. A device according to claim 1, in which said extension ofsaid tool holding means has a diameter less than that portion thereof which is adjacent said second cover.

3. A device according to claim 1, in which said impact piston includes surface means for closing off. said conduit means with regard to said auxiliary cylinder.

4. A hydraulically operable impact device which includes: a cylinder, a first cover closing one end of said cylinder, a second cover closing the other end of said cylinder, an impact piston reciprocable in said cylinder and having a blind hole substantially centrally located in that end face of said piston which faces toward said first cover, the bottom of said blind hole forming the impact stroke surface of said piston, said piston also being said accumulator, control valve means operable by said impact piston for controlling the supply of actuating fluid to and from said impact stroke surface and the end faces of said piston, and means comprising spring means yieldably connecting said second cover to said cylinder.

References Cited UNITED STATES PATENTS 1/1946 Fox 60-51 2,595,128 4/1952 Curtis 173134 2,674,850 4/1954 Svenson et al. 6051 2,980,079 4/ 1961 Joelson 6051 3,186,169 1/1965 Hauser 60-51 WILLIAM L. FREEH, Primary Examiner US. Cl. X.-R. 91218 

